Fatal victims

In the frenetic social media traffic that followed the Marathon blasts, a photograph of the wide-eyed boy holding a hand-lettered sign — “No more hurting people. Peace” — became an international emblem of the the day’s horror. His mother and sister were also seriously injured at the site of the second bomb.

Campbell, who grew up in Medford and moved about a year ago to Arlington, was on Boylston Street near the Marathon finish line with her friend Karen when the first bomb went off. She was remembered as a hard worker who "was always right there if you needed her," her grandmother said.

Lu, 23, a Boston University graduate student from the northeastern Chinese city of Shenyang, was the third victim of the bombings and the last to be identified. Lu’s friends recalled her as a kind young woman with a passion for music who hoped to find love in America.

Sean Collier, 26, was shot multiple times in a late-night confrontation with, officials believe, the two men responsible for the Boston Marathon bombings. He was known for having a knack for earning people’s trust, and for building rapport with the community he policed.

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